Some email-related web apps (such as webmail or antispam) can provide a part of their functionality directly in your Customer Panel. For example, you can associate a mail account with an account in the Open-Xchange webmail. In this case, the mail user will see the link to webmail in their Customer Panel.
To integrate an app in such a way, you should allow the app to access a certain mail account. You can do this in the mail account settings during the account creation or editing.
To allow certain apps to access an email account:
To deny certain apps to access an email account: